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Oral health is crucial to overall health, and periodontal disease (PDD) is a chronic inflammatory disease. Over the past decade, PDD has been recognized as a significant contributor to systemic inflammation. Here, we relate our seminal work defining the role of lysophosphatidic acid (LPA) and its receptors (LPARs) in the oral system with findings and parallels relevant to cancer. We discuss the largely unexplored fine-tuning potential of LPA species for biological control of complex immune responses and suggest approaches for the areas where we believe more research should be undertaken to advance our understanding of signaling at the level of the cellular microenvironment in biological processes where LPA is a key player so we can better treat diseases such as PDD, cancer, and emerging diseases.

Mast cells (MCs) are the main participants in the control of immune reactions associated with inflammation, allergies, defense against pathogens, and tumor growth. Bioactive lipids are lipophilic compounds able to modulate MC activation. Here, we explored some of the effects of the bioactive lipid lysophosphatidylinositol (LPI) on MCs. Utilizing murine bone marrow-derived mast cells (BMMCs), we found that LPI did not cause degranulation, but slightly increased FcεRI-dependent β-hexosaminidase release. However, LPI induced strong chemotaxis together with changes in LIM kinase (LIMK) and cofilin phosphorylation. LPI also promoted modifications to actin cytoskeleton dynamics that were detected by an increase in cell size and interruptions in the continuity of the cortical actin ring. The chemotaxis and cortical actin ring changes were dependent on GPR55 receptor activation, since the specific agonist O1602 mimicked the effects of LPI and the selective antagonist ML193 prevented them. The LPI and O1602-dependent stimulation of BMMC also led to VEGF, TNF, IL-1α, and IL-1β mRNA accumulation, but, in contrast with chemotaxis-related processes, the effects on cytokine transcription were dependent on GPR55 and cannabinoid (CB) 2 receptors, since they were sensitive to ML193 and to the specific CB2 receptor antagonist AM630. Remarkably, GPR55-dependent BMMC chemotaxis was observed towards conditioned media from distinct mouse and human cancer cells. Our data suggest that LPI induces the chemotaxis of MCs and leads to cytokine production in MC in vitro with the differential participation of GPR55 and CB2 receptors. These effects could play a significant role in the recruitment of MCs to tumors and the production of MC-derived pro-angiogenic factors in the tumor microenvironment.

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid that regulates fundamental cellular processes such as proliferation, migration, apoptosis, and differentiation through 5 cognate G protein-coupled receptors (S1P1-S1P5). We previously demonstrated that blockade of S1P2 signaling in S1P2-deficient mice attenuates high-fat diet-induced adipocyte hypertrophy and glucose intolerance and an S1P2-specific antagonist JTE-013 inhibits, whereas an S1P1/S1P3 dual antagonist (VPC23019) activates, adipogenic differentiation of preadipocytes. Based on those observations, this study examined whether an S1P1-specific agonist, SEW-2871, VPC23019, or their combination acts on obesity and glucose intolerance in leptin-deficient ob/ob mice. The oral administration of SEW-2871 or JTE-013 induced significant reductions in body/epididymal fat weight gains and epididymal/inguinal fat adipocyte sizes and improved glucose intolerance and adipocyte inflammation in ob/ob mice but not in their control C57BL/6J mice. Both SEW-2871 and JTE-013 decreased messenger RNA levels of tumor necrosis factor-α and CD11c, whereas they increased those of CD206 and adiponectin in the epididymal fats isolated from ob/ob mice with no changes in the levels of peroxisome proliferator activated receptor γ and its regulated genes. By contrast, VPC23019 did not cause any such alterations but counteracted with all those SEW-2871 actions in these mice. In conclusion, the S1P1 agonist SEW-2871 acted like the S1P2 antagonist JTE-013 to reduce body/epididymal fats and improve glucose tolerance in obese mice. Therefore, this study raises the possibility that endogenous S1P could promote obesity/type 2 diabetes through the S1P2, whereas exogenous S1P could act against them through the S1P1., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Endocrine Society.)

Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial pneumonias. Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are signaling lipids that evoke growth factor-like responses to many cells. Recent studies revealed the involvement of LPA and S1P in the pathology of IPF. In this study, we determined LPA, S1P and ceramide 1-phosphate (C1P) in peripheral blood plasma of IPF patients, and examined correlation to the vital capacity of lung (VC), an indicator of development of fibrosis. Blood plasma samples were taken from eleven patients with IPF and seven healthy volunteers. The lipids of the sample were extracted and subjected to liquid chromatography-tandem mass spectrometry for analysis. Results showed that there is a significant negative correlation between VC and plasma LPA levels, indicating that IPF patients with advanced fibrosis had higher concentration of LPA in their plasma. Average of S1P levels were significantly higher in IPF patients than those in healthy subjects. Although it is not statistically significant, a similar correlation trend that observed in LPA levels also found between VC and S1P levels. These results indicated that plasma LPA and S1P may be associated with deterioration of pulmonary function of IPF patients. J. Med. Invest. 69 : 196-203, August, 2022.

Sunitinib resistance is a major challenge in systemic therapy for renal cell carcinoma (RCC). The role of circular RNAs (circRNAs) in regulating sunitinib resistance of RCC is largely unknown. We established sunitinib-resistant RCC cell lines in vivo. Through RNA-sequencing, we identified circSNX6, whose expression is upregulated in sunitinib-resistant cells compared with their parental cells. High circSNX6 expression was correlated with sunitinib resistance and worse oncologic outcomes in a cohort of 81 RCC patients. In vitro and in vivo experiments confirmed that circSNX6 could promote sunitinib resistance in RCC. circSNX6 acts as a molecular "sponge" to relieve the suppressive effect of microRNA (miR)-1184 on its target gene, glycerophosphocholine phosphodiesterase 1 (GPCPD1), which increases intracellular lysophosphatidic acid (LPA) levels and, ultimately, promotes sunitinib resistance in RCC cells. Our findings demonstrated that the circSNX6/miR-1184/GPCPD1 axis had a critical role in regulation of intracellular LPA levels and sunitinib resistance in RCC; they also provide a novel prognostic indicator and promising therapeutic targets., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Accumulating evidence indicates that the molecular pathways mediating wound healing induce cell migration and localization of cytokines to sites of injury. Macrophages are immune cells that sense and actively respond to disturbances in tissue homeostasis by initiating, and subsequently resolving, inflammation. Hypoxic conditions generated at a wound site also strongly recruit macrophages and affect their function. Hypoxia inducible factor (HIF)-1α is a transcription factor that contributes to both glycolysis and the induction of inflammatory genes, while also being critical for macrophage activation. For the latter, HIF-1α regulates sphingosine 1-phosphate (S1P) to affect the migration, activation, differentiation, and polarization of macrophages. Recently, S1P and HIF-1α have received much attention, and various studies have been performed to investigate their roles in initiating and resolving inflammation via macrophages. It is hypothesized that the HIF-1α/S1P/S1P receptor axis is an important determinant of macrophage function under inflammatory conditions and during disease pathogenesis. Therefore, in this review, biological regulation of monocytes/macrophages in response to circulating HIF-1α is summarized, including signaling by S1P/S1P receptors, which have essential roles in wound healing.

For decades, lipids were confined to the field of structural biology and energetics as they were considered only structural constituents of cellular membranes and efficient sources of energy production. However, with advances in our understanding in lipidomics and improvements in the technological approaches, astounding discoveries have been made in exploring the role of lipids as signaling molecules, termed bioactive lipids. Among these bioactive lipids, sphingolipids have emerged as distinctive mediators of various cellular processes, ranging from cell growth and proliferation to cellular apoptosis, executing immune responses to regulating inflammation. Recent studies have made it clear that sphingolipids, their metabolic intermediates (ceramide, sphingosine-1-phosphate, and N-acetyl sphingosine), and enzyme systems (cyclooxygenases, sphingosine kinases, and sphingomyelinase) harbor diverse yet interconnected signaling pathways in the central nervous system (CNS), orchestrate CNS physiological processes, and participate in a plethora of neuroinflammatory and neurodegenerative disorders. Considering the unequivocal importance of sphingolipids in CNS, we review the recent discoveries detailing the major enzymes involved in sphingolipid metabolism (particularly sphingosine kinase 1), novel metabolic intermediates (N-acetyl sphingosine), and their complex interactions in CNS physiology, disruption of their functionality in neurodegenerative disorders, and therapeutic strategies targeting sphingolipids for improved drug approaches.

Breast cancer stem cells (BCSCs) are essential for cancer growth, metastasis and recurrence. The regulatory mechanisms of BCSC interactions with the vascular niche within the tumor microenvironment (TME) and their self-renewal are currently under extensive investigation. We have demonstrated the existence of an arteriolar niche in the TME of human BC tissues. Intriguingly, BCSCs tend to be enriched within the arteriolar niche in human estrogen receptor positive (ER + ) BC and bi-directionally interact with arteriolar endothelial cells (ECs). Mechanistically, this interaction is driven by the lysophosphatidic acid (LPA)/protein kinase D (PKD-1) signaling pathway, which promotes both arteriolar differentiation of ECs and self-renewal of CSCs likely via differential regulation of CD36 transcription. This study indicates that CSCs may enjoy blood perfusion to maintain their stemness features. Targeting the LPA/PKD-1 -CD36 signaling pathway may have therapeutic potential to curb tumor progression by disrupting the arteriolar niche and effectively eliminating CSCs.

In malaria-endemic countries, the burden of hypertension is on the rise. Although malaria and hypertension seem to have no direct link, several studies in recent years support their possible link. Three bioactive molecules such as angiotensin II (Ang II), bradykinin (BK) and sphingosine 1-phosphate (S1P) are crucial in regulating blood pressure. While the increased level of Ang II and S1P are responsible for inducing hypertension, BK is arthero-protective and anti-hypertensive. Therefore, in the present review, based on available literatures we highlight the present knowledge on the production and bioavailability of these molecules, the mechanism of their regulation of hypertension, and patho-physiological role in malaria. Further, a possible link between malaria and hypertension is hypothesized through various arguments based on experimental evidence. Understanding of their mechanisms of blood pressure regulation during malaria infection may open up avenues for drug therapeutics and management of malaria in co-morbidity with hypertension.

Sphingosine 1-phosphate (S1P) is an important lipid biomolecule that exerts pleiotropic cellular actions as it binds to and activates its five G-protein-coupled receptors, S1P 1-5 . Through these receptors, S1P can mediate diverse biological activities in both healthy and diseased conditions. S1P is produced by S1P-producing enzymes, sphingosine kinases (SphK1 and SphK2), and is abundantly present in different organs, including the brain. The medically important roles of receptor-mediated S1P signaling are well characterized in multiple sclerosis because FTY720 (Gilenya™, Novartis), a non-selective S1P receptor modulator, is currently used as a treatment for this disease. In cerebral ischemia, its role is also notable because of FTY720's efficacy in both rodent models and human patients with cerebral ischemia. In particular, some of the S1P receptors, including S1P 1 , S1P 2 , and S1P 3 , have been identified as pathogenic players in cerebral ischemia. Other than these receptors, S1P itself and S1P-producing enzymes have been shown to play certain roles in cerebral ischemia. This review aims to compile the current updates and overviews about the roles of S1P signaling, along with a focus on S1P receptors in cerebral ischemia, based on recent studies that used in vivo rodent models of cerebral ischemia.

Sphingosine 1-phosphates (S1Ps) are bioactive lipids that mediate a diverse range of effects through the activation of cognate receptors, S1P 1 -S1P 5 . Scrutiny of S1P-regulated pathways over the past three decades has identified important and occasionally counteracting functions in the brain and cerebrovascular system. For example, while S1P 1 and S1P 3 mediate proinflammatory effects on glial cells and directly promote endothelial cell barrier integrity, S1P 2 is anti-inflammatory but disrupts barrier integrity. Cumulatively, there is significant preclinical evidence implicating critical roles for this pathway in regulating processes that drive cerebrovascular disease and vascular dementia, both being part of the continuum of vascular cognitive impairment (VCI). This is supported by clinical studies that have identified correlations between alterations of S1P and cognitive deficits. We review studies which proposed and evaluated potential mechanisms by which such alterations contribute to pathological S1P signaling that leads to VCI-associated chronic neuroinflammation and neurodegeneration. Notably, S1P receptors have divergent but overlapping expression patterns and demonstrate complex interactions. Therefore, the net effect produced by S1P represents the cumulative contributions of S1P receptors acting additively, synergistically, or antagonistically on the neural, vascular, and immune cells of the brain. Ultimately, an optimized therapeutic strategy that targets S1P signaling will have to consider these complex interactions.

Objectives: This study was designed to explore the intellectual landscape of research into the application of sphingosine 1 phosphate (S1P) in age-related diseases and to identify thematic development trends and research frontiers in this area., Methods: Scientometric research was conducted by analyzing bibliographic records retrieved from the Web of Science (WOS) Sci-Expanded Database dated between 1900 and 2020. Countries, institutions, authors, keyword occurrence analysis, and cooperation network analysis were performed using the CiteSpace and VOSviewer software., Results: A total of 348 valid records were included in the final dataset, and the number of publications and the frequency of citations have grown rapidly over the last ten years. The USA ( n = 175), China ( n = 42), and Germany ( n = 37) were the three largest contributors to the global publications on S1P and aging, while the Medical University of South Carolina ( n = 15), University of California, San Francisco ( n = 13), and University of Toronto ( n = 13) were the leading institutions in this field. Analysis showed that early studies primarily focused on the mechanism of S1P intervention in AD. While S1P and its relevant metabolites have remained a long-term active area of research, recent studies have focused more on interventions aimed at improving retinal degeneration, cardiomyopathy, multiple sclerosis, and diabetes, among others., Conclusions: It is worth mentioning that this manuscript is the first to describe any bibliometric analysis of S1P and its application in age-related interventions. This study includes a discussion of the (1) historical overview of the topic; (2) main contributors: journals, countries, institutes, funding agencies, and authors; (3) collaboration between institutes and authors; (4) research hot spots and zones; and 5) research trends and frontiers. This will enable scholars to understand the current status of S1P research in age-related diseases., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2021 Qiong He et al.)

Transfusion-related acute lung injury (TRALI) is a hazardous transfusion complication with an associated mortality of 5% to 15%. We previously showed that stored (5 days) but not fresh platelets (1 day) cause TRALI via ceramide-mediated endothelial barrier dysfunction. As biological ceramides are hydrophobic, extracellular vesicles (EVs) may be required to shuttle these sphingolipids from platelets to endothelial cells. Adding to complexity, EV formation in turn requires ceramide. We hypothesized that ceramide-dependent EV formation from stored platelets and EV-dependent sphingolipid shuttling induces TRALI. EVs formed during storage of murine platelets were enumerated, characterized for sphingolipids, and applied in a murine TRALI model in vivo and for endothelial barrier assessment in vitro. Five-day EVs were more abundant, had higher long-chain ceramide (C16:0, C18:0, C20:0), and lower sphingosine-1-phosphate (S1P) content than 1-day EVs. Transfusion of 5-day, but not 1-day, EVs induced characteristic signs of lung injury in vivo and endothelial barrier disruption in vitro. Inhibition or supplementation of ceramide-forming sphingomyelinase reduced or enhanced the formation of EVs, respectively, but did not alter the injuriousness per individual EV. Barrier failure was attenuated when EVs were abundant in or supplemented with S1P. Stored human platelet 4-day EVs were more numerous compared with 2-day EVs, contained more long-chain ceramide and less S1P, and caused more endothelial cell barrier leak. Hence, platelet-derived EVs become more numerous and more injurious (more long-chain ceramide, less S1P) during storage. Blockade of sphingomyelinase, EV elimination, or supplementation of S1P during platelet storage may present promising strategies for TRALI prevention., (© 2021 by The American Society of Hematology.)

Lipidomics is a lipid-targeted metabolomics approach that aims to the comprehensive analysis of lipids in biological systems in order to highlight the specific functions of lipid species in health and disease. Lipids play pivotal roles as they are major structural components of the cellular membranes and energy storage molecules but also, as most recently shown, they act as functional and regulatory components of intra- and intercellular signaling. Herein, emphasis is given to the recently highlighted roles of specific bioactive lipids species, as polyunsaturated fatty acids (PUFA)-derived mediators (generally known as eicosanoids), endocannabinoids (eCBs), and lysophospholipids (LPLs), and their involvement in the mesenchymal stem cells (MSCs)-related inflammatory scenario. Indeed, MSCs are a heterogenous population of multipotent cells that have attracted much attention for their potential in regulating inflammation, immunomodulatory capabilities, and reparative roles. The lipidomics of the inflammatory disease osteoarthritis (OA) and the influence of MSCs-derived lipids have also been addressed.

Alzheimer's disease (AD) is the leading cause of dementia worldwide giving rise to devastating forms of cognitive decline, which impacts patients' lives and that of their proxies. Pathologically, AD is characterized by extracellular amyloid deposition, neurofibrillary tangles and chronic neuroinflammation. To date, there is no cure that prevents progression of AD. In this review, we elaborate on how bioactive lipids, including sphingolipids (SL) and specialized pro-resolving lipid mediators (SPM), affect ongoing neuroinflammatory processes during AD and how we may exploit them for the development of new biomarker panels and/or therapies. In particular, we here describe how SPM and SL metabolism, ranging from ω-3/6 polyunsaturated fatty acids and their metabolites to ceramides and sphingosine-1-phosphate, initiates pro- and anti-inflammatory signaling cascades in the central nervous system (CNS) and what changes occur therein during AD pathology. Finally, we discuss novel therapeutic approaches to resolve chronic neuroinflammation in AD by modulating the SPM and SL pathways., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 de Wit, Mol, Rodríguez-Lorenzo, de Vries and Kooij.)

Lipids are abundant and play essential roles in human health and disease. The main functions of lipids are building blocks for membrane biogenesis. However, lipids are also metabolized to produce signaling molecules. Here, we discuss the emerging roles of circulating lysophospholipids. These lysophospholipids consist of lysoglycerophospholipids and lysosphingolipids. They are both present in cells at low concentration, but their concentrations in extracellular fluids are significantly higher. The biological functions of some of these lysophospholipids have been recently revealed. Remarkably, some of the lysophospholipids play pivotal signaling roles as well as being precursors for membrane biogenesis. Revealing how circulating lysophospholipids are produced, released, transported, and utilized in multi-organ systems is critical to understand their functions. The discovery of enzymes, carriers, transporters, and membrane receptors for these lysophospholipids has shed light on their physiological significance. In this review, we summarize the biological roles of these lysophospholipids via discussing about the proteins regulating their functions. We also discuss about their potential impacts to human health and diseases., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Breast cancer is one of the most common female malignant cancers. Biorhythm disorder largely increases the risk of breast cancer. We aimed to investigate the biological functions and molecular mechanisms of circadian gene TIMELESS circadian regulator (TIM) in estrogen receptor (ER)-positive breast cancer and provide a new therapeutic target for breast cancer patients. Here, we explored that the expression of TIM was elevated in breast cancer, and high expression of TIM in cancer tissues was associated with poor prognosis, especially in the ER-positive breast cancer patients. In addition, we found that TIM promoted cell proliferation and enhanced mitochondrial respiration. TIM interacted with specificity protein 1 (Sp1) which contributes to upregulate the expression of alkaline ceramidase 2 (ACER2). Moreover, ACER2 is responsible for TIM-mediated promotive effects of cell growth and mitochondrial respiration. Collectively, our research unveiled a novel function of TIM in sphingolipid metabolism through interaction with Sp1. It provides a new theoretical explanation for the pathogenesis of breast cancer, and targeting TIM may serve as a potential therapeutic target for ER-positive breast cancer.

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, in which the immune system attacks synovial joint tissues. Interleukin (IL)-1β is a critical proinflammatory cytokine in RA progression. Sphingosine-1-phosphate (S1P), a platelet-derived lysophospholipid mediator, reportedly regulates osteoimmunology. Here, we investigated how S1P mediates IL-1β expression in osteoblasts. Our analysis of records from the Gene Expression Omnibus (GEO) database demonstrate higher levels of IL-1β in patients with RA compared with those with osteoarthritis. Stimulation of osteoblasts with S1P concentration dependently increased mRNA and protein expression of IL-1β. Elevations in IL-1β mRNA expression induced by S1P were reduced by the small interfering RNA (siRNA) against the S1P 1 receptor. S1P also augmented JAK and STAT3 molecular cascades. We also found that JAK and STAT3 inhibitors and their siRNAs antagonized S1P-promoted IL-1β expression. Our results indicate that S1P promotes the expression of IL-1β in osteoblasts via the S1P 1 receptor and the JAK and STAT3 signaling pathways., (© 2020 Wiley Periodicals, Inc.)

Background: Baicalein has been shown to have anti-inflammatory and anti-tumor activities. However, the mechanisms underlying its anti-inflammatory effect on colitis remain unclear., Methods: A dextran sodium sulfate (DSS)-induced model of acute colitis was established in BALB/c mice (6-8 weeks old, weighing 18-22 g). Six groups of mice received: (1) water for 10 days (control), n = 6; (2) DSS 4% solution in the drinking water for 7 days, followed by normal water for 3 days, n = 7; (3), (4), and (5) as for group 2 plus baicalein (10, 20, 40 mg/kg) administered once daily starting on day 1, n = 6; and (6) as for (2) plus 5-aminosalicylic acid (50 mg/kg) administered once daily starting on day 1, n = 6. Body weights, stool consistency, and hematochezia were recorded, and the severity of colitis was evaluated using a disease activity index. On day 11, the mice were euthanized, and organs and blood were collected for analysis. Serum inflammatory factors were detected by enzyme-linked immunosorbent assay; CD11b-positive cells were analyzed by immunofluorescence microscopy; expression of retinoic-acid-receptor-related orphan nuclear receptor gamma, sphingosine kinase 1 (SPHK1), and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) was detected by immunohistochemistry; and expression of nucleotide-binding oligomerization domain 2 (NOD2), SPHK1, sphingosine 1-phosphate receptor 1 (S1PR1), total STAT3, and p-STAT3 were detected by western blotting analysis. Inter-group differences were compared using Student's t test., Results: Baicalein treatment dose-dependently reduced DSS-induced weight loss (P < 0.01 or P < 0.05), splenomegaly (P < 0.01), and colonic damage, as reflected by amelioration of diarrhea, rectal bleeding, and colonic ulceration, congestion, edema (shown as colon length, P < 0.05 or P < 0.01), and inflammatory cell infiltration. Baicalein also significantly decreased the levels of inflammatory mediators in the serum (P < 0.01) and colon, and significantly inhibited expression of NOD2 SPHK1, S1PR1, and p-STAT3 in the colon (P < 0.05)., Conclusions: Baicalein treatment ameliorated colitis in mice by inhibiting S1P-STAT3 signaling, suggesting that this flavonoid might be beneficial in the treatment of colitis.

Sphingosine-1-phoshate (S1P) is a membrane sphingolipid involved in several physiological processes, including cell proliferation, tissue growth, cell survival and migration, inflammation, vasculogenesis, and angiogenesis. Herein, we review the most critical effects of S1P on ovarian function, including its physiological and pathophysiological effects. Based on the available evidence, S1P plays an important role in ovarian physiology, participating as an essential stimulator of follicular development in both the preantral and antral phases, as well as in ovulation and corpus luteum development. Moreover, S1P may be a good cytoprotective agent against cancer treatment side-effects (chemotherapy with or without radiation therapy). In the future, this compound may be given for fertility preservation to women undergoing cancer treatment. However, further studies are required to confirm its efficacy in ovarian protection and also its safety in terms of cancer prognosis, given the biological action of the compound. Under- or over-production of S1P may be related to ovarian pathologies., (Copyright © 2019. Published by Elsevier Masson SAS.)

Despite decades of therapeutic advances, myocardial infarction remains a leading cause of death worldwide. Recent studies have identified HDLs (high-density lipoproteins) as a potential candidate for mitigating coronary ischemia/reperfusion injury via a broad spectrum of signaling pathways. HDL ligands, such as S1P (sphingosine-1-phosphate), Apo (apolipoprotein) A-I, clusterin, and miRNA, may influence the opening of the mitochondrial channel, insulin sensitivity, and production of vascular autacoids, such as NO, prostacyclin, and endothelin-1. In parallel, antioxidant activity and sequestration of oxidized molecules provided by HDL can attenuate the oxidative stress that triggers ischemia/reperfusion. Nevertheless, during myocardial infarction, oxidation and the capture of oxidized and proinflammatory molecules generate large phenotypic and functional changes in HDL, potentially limiting its beneficial properties. In this review, new findings from cellular and animal models, as well as from clinical studies, will be discussed to describe the cardioprotective benefits of HDL on myocardial infarction. Furthermore, mechanisms by which HDL modulates cardiac function and potential strategies to mitigate postmyocardial infarction risk damage by HDL will be detailed throughout the review.

Integrin β6 (ITGB6), an epithelial-specific integrin, is upregulated in oral squamous cell carcinomas (OSCC) and is associated with progression and metastasis of OSCC. Lysophosphatidic acid (LPA), an important bioactive phospholipid present in saliva, has also been related to OSCC cell migration and invasiveness. LPA exerts its biological effects through signal transduction pathways that ultimately regulate gene expression. However, it is unclear whether LPA signaling is involved in ITGB6 upregulation in OSCC. Therefore, the aim of the current study was to investigate the role of LPA in the regulation of ITGB6 expression in OSCC cells, and to delineate the molecular signaling pathways involved. Using SAS and HSC-3 OSCC cell lines, we found that LPA increases ITGB6 mRNA expression without affecting mRNA stability, suggesting that LPA acts by regulating ITGB6 gene transcription. In addition, we show that LPA stimulation increases phosphorylation and binding of the transcription factors SMAD3 and ETS-1 to the ITGB6 promoter resulting in ITGB6 active transcription. Finally, we demonstrate that LPA-induced ITGB6 expression is mediated via the LPA receptors 1 (LPAR1) coupling to Gα i . Our findings provide insights into the molecular mechanism underlying ITGB6 overexpression in OSCC and may have important implications for therapeutic purposes., (Copyright © 2019 Elsevier Inc. All rights reserved.)

A role of sphingolipids for inflammatory bowel disease and cancer is evident. However, the relative and separate contribution of sphingolipid deterioration in inflammation versus carcinogenesis for the pathophysiology of colitis-associated colon cancer (CAC) was unknown and therefore examined in this study. We performed isogenic bone marrow transplantation of inducible sphingosine-1-phosphate (S1P) lyase knockout mice to specifically modulate sphingolipids and associated genes and proteins in a compartment-specific way in a DSS/AOM mediated CAC model. 3D organoid cultures were used in vitro. S1P lyase (SGPL1) knockout in either immune cells or tissue, caused local sphingolipid accumulation leading to a dichotomic development of CAC: Immune cell SGPL1 knockout (I-SGPL -/- ) augmented massive immune cell infiltration initiating colitis with lesions and calprotectin increase. Pathological crypt remodeling plus extracellular S1P-signaling caused delayed tumor formation characterized by S1P receptor 1, STAT3 mRNA increase, as well as programmed cell death ligand 1 expression, accompanied by a putatively counter regulatory STAT1 S727 phosphorylation. In contrast, tissue SGPL1 knockout (T-SGPL -/- ) provoked immediate occurrence of epithelial-driven tumors with upregulated sphingosine kinase 1, S1P receptor 2 and epidermal growth factor receptor. Here, progressing carcinogenesis was accompanied by an IL-12 to IL-23 shift with a consecutive development of a T h 2/GATA3-driven, tumor-favoring microenvironment. Moreover, the knockout models showed distinct lymphopenia and neutrophilia, different from the full SGPL1 knockout. This study shows that depending on the initiating cellular S1P source, the pathophysiology of inflammation-induced cancer versus cancer-induced inflammation develops through separate, discernible molecular steps.

Epithelial-mesenchymal transition (EMT) is a critical process implicated in the initial stage of cancer metastasis, which is the major cause of tumor recurrence and mortality. Although key transcription factors that regulate EMT, such as snail family transcriptional repressor 2 (SNAI2), are well characterized, the upstream signaling pathways controlling these transcriptional mediators are largely unknown, which limits therapeutic strategies. Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator, generated by sphingosine kinases (SPHK1 and SPHK2), that mainly exerts its effects by binding to the following 5 GPCRs: S1P 1 to S1P 5 . S1P signaling has been reported to regulate different aspects of cancer progression including cell proliferation, apoptosis, and migration; nevertheless, its role in cancer metastasis, specifically via EMT, is not established. Here we show that SPHK1 expression correlates significantly with EMT score in breast cancer cell lines, and with SNAI2 in patient-derived breast tumors. Cell-based assays demonstrate that S1P can rapidly up-regulate the expression of SNAI2 in breast cancer cells via the activation of cognate receptors S1P 2 and S1P 3 . Knockdown studies suggest that S1P 2 and S1P 3 mediate this effect by activating myocardin-related transcription factor A (MRTF-A) and yes-associated protein (YAP), respectively. Michigan Cancer Foundation 7 cells stably overexpressing S1P 2 or S1P 3 exhibit a more invasive phenotype, when compared to control cells. Taken together, our findings suggest that S1P produced by SPHK1 induces SNAI2 expression via S1P 2 -YAP and S1P 3 -MRTF-A pathways, leading to enhanced cell invasion. Cumulatively, this study reveals a novel mechanism by which S1P activates parallel pathways that regulate the expression of SNAI2, a master regulator of EMT, and provides new insights into druggable therapeutic targets that may limit cancer metastasis. Wang, W., Hind, T., Lam, B. W. S., Herr, D. R. Sphingosine 1-phosphate signaling induces SNAI2 expression to promote cell invasion in breast cancer cells.

Hearing loss is among the most prevalent sensory impairments in humans. Cochlear implantable devices represent the current therapies for hearing loss but have various shortcomings. ERM (ezrin- radixin -moesin) are a family of adaptor proteins that link plasma membrane with actin cytoskeleton, playing a crucial role in cell morphology and in the formation of membrane protrusions. Recently, bioactive sphingolipids have emerged as regulators of ERM proteins. Sphingosine 1-phosphate (S1P) is a pleiotropic sphingolipid which regulates fundamental cellular functions such as proliferation, survival, migration as well as processes such as development and inflammation mainly via ligation to its specific receptors S1PR (S1P 1-5 ). Experimental findings demonstrate a key role for S1P signaling axis in the maintenance of auditory function. Preservation of cellular junctions is a fundamental function both for S1P and ERM proteins, crucial for the maintenance of cochlear integrity. In the present work, S1P was found to activate ERM in a S1P 2 -dependent manner in murine auditory epithelial progenitors US/VOT-E36. S1P-induced ERM activation potently contributed to actin cytoskeletal remodeling and to the appearance of ionic currents and membrane passive properties changes typical of more differentiated cells. Moreover, PKC and Akt activation was found to mediate S1P-induced ERM phosphorylation. The obtained findings contribute to demonstrate the role of S1P signaling pathway in inner ear biology and to disclose potential innovative therapeutical approaches in the field of hearing loss prevention and treatment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Bone is a highly dynamic organ that is continuously being remodeled by the reciprocal interactions between bone and immune cells. We have originally established an advanced imaging system for visualizing the in vivo behavior of osteoclasts and their precursors in the bone marrow cavity using two-photon microscopy. Using this system, we found that the blood-enriched lipid mediator, sphingosine-1-phosphate, controlled the migratory behavior of osteoclast precursors. We also developed pH-sensing chemical fluorescent probes to detect localized acidification by bone-resorbing osteoclasts on the bone surface in vivo , and identified two distinct functional states of differentiated osteoclasts, "bone-resorptive" and "non-resorptive." Here, we summarize our studies on the dynamics and functions of bone and immune cells within the bone marrow. We further discuss how our intravital imaging techniques can be applied to evaluate the mechanisms of action of biological agents in inflammatory bone destruction. Our intravital imaging techniques would be beneficial for studying the cellular dynamics in arthritic inflammation and bone destruction in vivo and would also be useful for evaluating novel therapies in animal models of bone-destroying diseases.

Lysophosphatidic acid (LPA) is the simplest phospholipid found in nature. LPA is mainly biosynthesized in tissues and cells by autotoxin and PA-PLA1α/PA-PLA1β and is degraded by lipid phosphate phosphatases (LPPs). It is an important component of biofilm, an extracellular signal transmitter and intracellular second messenger. After targeting to endothelial differentiation gene (Edg) family LPA receptors (LPA1, LPA2, LPA3) and non-Edg family LPA receptors (LPA4, LPA5, LPA6), LPA mediates physiological and pathological processes such as embryonic development, angiogenesis, tumor progression, fibrogenesis, wound healing, ischemia/reperfusion injury, and inflammatory reactions. These processes are induced through signaling pathways including mitogen-activated protein kinase (MAPK), phosphatidylinositol-3-kinase (PI3K)/Akt, protein kinase C (PKC)-GSK3β-β-catenin, Rho, Stat, and hypoxia-inducible factor 1-alpha (HIF-1α). LPA is involved in multiple physiological and pathological processes in the skin. It not only regulates skin function but also plays an important role in hair follicle development, skin wound healing, pruritus, skin tumors, and scleroderma. Pharmacological inhibition of LPA synthesis or antagonization of LPA receptors is a new strategy for the treatment of various skin disorders. This review focuses on the current understanding of the pathophysiologic role of LPA in the skin., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Key homeostatic functions are regulated in a diurnal manner and a miss-alignment of such rhythms is believed to contribute to the pathophysiology of several diseases. Signaling sphingolipids (SLs) in plasma such as sphingosine 1-phosphate control lymphocytic trafficking, vascular reactivity and platelet activity, physiological functions all of which display a diurnal rhythm themselves. However, the rhythmicity of SL metabolism in plasma and its potential causes have not been sufficiently investigated so far. Therefore, we analyzed blood of mice and healthy adult human subjects by targeted tandem mass-spectrometry at different time points. In order to investigate the influence of the synchronizing hormone melatonin, we compared melatonin proficient C3H/HeN wildtype mice (C3H) with melatonin receptor-1/2 double knockout mice (MT1/2-/-) and melatonin deficient C57BL/6J mice. We found a strong upregulation of plasma S1P with the beginning of the light period in C3H but not in MT1/2-/- or C57BL/6J mice. Accordingly, our study revealed an upregulation of sphingosine 1-phosphate (S1P d18:1) and sphinganine 1-phosphate (S1P d18:0) with the beginning of the light period in humans. Furthermore, plasma S1P d18:1 and S1P d18:0 were inversely correlated with the respective concentrations in platelets, pointing to a possible involvement of platelet SL metabolism. In humans, the diurnal rhythm of SLs was not associated with changes of SL-binding proteins or counts of cellular SL sources. Overall, this study indicates a physiological rhythmicity of plasma and platelet SL metabolism, likely mediated by melatonin, with potentially important implications for physiological diurnal rhythms and the regulation of SL metabolism and its functions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: S1P has known endothelial barrier-protective properties, but whether this extends to the BBB is unclear. We hypothesized that alcohol-induced disruption of brain microvascular endothelial barrier function and junctional protein organization can be ameliorated by S1P treatment., Methods: Cultured primary HBMEC monolayers were used to characterize endothelial-specific mechanisms of BBB regulation. TER and apparent permeability coefficients for albumin, dextran-4 kDa, and sodium fluorescein were used as indices of barrier function. Junctional localization of Claudin-5, VE-cadherin, and β-catenin was determined by immunofluorescence confocal microscopy. S1P was applied following treatment with alcohol., Results: Alcohol significantly impaired HBMEC TER. Application of S1P after alcohol treatment resulted in a hastened recovery to the baseline HBMEC TER. Alcohol-treated HBMEC had a significantly higher mean permeability than control that was reversed by S1P. Alcohol caused the formation of gaps between cells. Treatment with S1P (after alcohol) increased junctional localization of VE-Cadherin, Claudin-5, and β-catenin., Conclusions: Alcohol impairs the barrier function and junctional organization of HBMEC monolayers. S1P enhanced barrier function and restored junctions in the presence of alcohol, and thus may be useful for restoring BBB function during alcohol intoxication., (© 2018 John Wiley & Sons Ltd.)

Background: Pancreatic cancer is a disease with poor prognosis, and development of new treatments is necessary. Sphingosine-1-phosphate (S1P), a bioactive lipid mediator produced by sphingosine kinases (SphK1 and SphK2), plays a critical role in progression of many types of cancer. However, little is known about the role of sphingosine kinases in pancreatic cancer. This study investigated the roles of sphingosine kinases in pancreatic cancer progression., Materials and Methods: S1P levels in pancreatic cancer and noncancerous pancreatic tissue were measured in 10 patients. We generated PAN02 murine pancreatic cancer cell lines with a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system genes 9 (Cas9)-mediated deletion of SphK1 or SphK2 and assessed cell growth and migration. In an animal model, we assessed the survival of mice injected with PAN02 cells intraperitoneally., Results: S1P levels in the pancreatic cancer tissue were significantly higher than those in noncancerous tissue. SphK1 knockout (KO) cells showed greater proliferation and migration than wild type (WT) cells, and SphK2 KO cells showed less proliferation and migration than WT cells. Animal experiments showed that the survival of mice injected with SphK1 KO cells was significantly shorter than those injected with WT cells, and the survival of mice injected with SphK2 KO cells was longer than those injected with WT cells. Surprisingly, cytotoxic assay using gemcitabine showed that SphK1 KO cells survived less than WT cells, and SphK2 KO cells survived more than WT cells., Conclusions: S1P produced by SphK1 and SphK2 may have different functions in pancreatic cancer cells. Targeting both SphK1 and SphK2 may be a potential strategy for pancreatic cancer treatment., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Cardiovascular diseases (CVD) remain the leading cause of death in industrialized countries. One of the most significant risk factors for atherosclerosis is hypercholesterolemia. Its diagnostics is based on routine lipid profile analysis, including the determination of total cholesterol, low and high density lipoprotein cholesterol, and triglycerides. However in recent years, much attention has been paid to the crosstalk between the metabolic pathways of the cholesterol and sphingolipids biosynthesis. Sphingolipids are a group of lipids, containing a molecule of aliphatic alcohol sphingosine. These include sphingomyelins, cerebrosides, gangliosides and ceramides, sphingosines, and sphingosine-1-phosphate (S-1-P). It has been found that catabolism of sphingolipids is associated with catabolism of cholesterol. However, the exact mechanism of this interaction is still unknown. Particular attention as CVD inducer attracts ceramide (Cer). Lipoprotein aggregates isolated from atherosclerotic pluques are enriched with Cer. The level of Cer and sphingosine increases after ischemia reperfusion of the heart, in the infarction zone and in the blood, and also in hypertension. S-1-P exhibits pronounced cardioprotective properties. Its content sharply decreases with ischemia and myocardial infarction. S-1-P presents predominantly in HDL, and influences their multiple functions. Increased levels of Cer and sphingosine and decreased levels of S-1-P formed in the course of coronary heart disease can be an important factor in the development of atherosclerosis. It is proposed to use determination of sphingolipids in blood plasma as markers for early diagnosis of cardiac ischemia and for hypertension in humans. There are intensive studies aimed at correction of metabolism S-1-P. The most successful drugs are those that use S-1-P receptors as a targets, since all of its actions are receptor-mediated.

Lysophosphatidic acid (LPA) is a small ubiquitous lipid exerting diverse biological functions. Its role in reproduction in different species has created great interest in recent times. In the present study, we aimed to elucidate LPA signaling in nonpregnant buffalo uterus by in vitro studies. Standard techniques like real-time PCR (for mRNA expression of LPARs and COX-2 and iNOS), Western blot (for PPARγ protein expression), sandwich ELISA (for PGE2 and PGF2α assay) and histopathology (for assessment of endometrial architecture in culture) were used in this study. The buffalo uterine tissues were collected from the local slaughterhouse and were selected for the study on the basis of the presence of corpus luteum on the ovary (n = 5). The LPAR3 receptor was the highest expressed receptor as compared to LPAR1 and LPAR6 in non-pregnant uterine tissues after 6 h incubation in Dulbecco's Modified Eagle Medium (DMEM). 50 μM LPA increased the mRNA expressions of COX-2 and iNOS enzymes which were attenuated by the treatment of LPAR1/3 antagonist Ki16425. PPARγ antagonist GW9662 prevented the LPA-induced increase in iNOS mRNA expression but did not alter the COX-2 expression. LPA also enhanced the PGE 2 to PGF 2α ratio in uterine tissue homogenates which was inhibited by all the receptor antagonists as well as by the inhibitors of COX-2 and iNOS. LPA also increased the total nitrite level in tissue homogenates in LPAR1/3- and iNOS-dependent manner. Additionally, we demonstrate PPARγ mRNA and protein expressions in nonpregnant buffalo endometrium. In conclusion, the results of the present study suggest that LPA acts as a luteotropic factor during the estrus cycle in nonpregnant buffalo uterus by enhancing PGE2 to PGF2α ratio and NO level through multiple receptors., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Stem cells are unique in their ability to self-renew and differentiate into various cell types. Because of these features, stem cells are key to the formation of organisms and play fundamental roles in tissue regeneration and repair. Mechanisms controlling their fate are thus fundamental to the development and homeostasis of tissues and organs. Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are bioactive phospholipids that play a wide range of roles in multiple cell types, during developmental and pathophysiological events. Considerable evidence now demonstrates the potent roles of LPA and S1P in the biology of pluripotent and adult stem cells, from maintenance to repair. Here we review their roles for each main category of stem cells and explore how those effects impact development and physiopathology., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: Obesity and obesity-related metabolic disorders are major health problems worldwide. The most effective obesity intervention is bariatric surgery. This study tested the hypothesis that bariatric surgery alters phospholipid metabolism in the gastrointestinal tract to favor a metabolically healthy gut microbiota profile and therapeutic intervention of phospholipid metabolism in the gastrointestinal may have similar metabolic benefits., Methods: The first study compared plasma levels of the bioactive lipid metabolites lysophospholipid and trimethylamine N-oxide (TMAO) as well as gut microbiota profile in high fat/carbohydrate (HFHC) diet-fed C57BL/6 mice with or without vertical sleeve gastrectomy (VSG) and in Pla2g1b -/- mice with group 1B phospholipase A 2 gene inactivation. The second study examined the effectiveness of the non-absorbable secretory phospholipase A 2 inhibitor methyl indoxam to reverse hyperglycemia and hyperlipidemia in HFHC diet-fed C57BL/6 mice after diabetes onset., Results: Both bariatric surgery and PLA2G1B inactivation were shown to reduce lysophospholipid content in the gastrointestinal tract, resulting in resistance to HFHC diet-induced alterations of the gut microbiota, reduction of the cardiovascular risk factors hyperlipidemia and TMAO, decreased adiposity, and prevention of HFHC diet-induced diabetes. Importantly, treatment of wild type mice with methyl indoxam after HFHC diet-induced onset of hyperlipidemia and hyperglycemia effectively restored normal plasma lipid and glucose levels and replicated the metabolic benefits of VSG surgery with diabetes remission and TMAO reduction., Conclusion: These results provided pre-clinical evidence that PLA2G1B inhibition in the digestive tract may be a viable alternative option to bariatric surgery for obesity and obesity-related cardiometabolic disorder intervention., (Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.)

A concomitant action of multiple profibrotic mediators appears crucial in the development and progression of fibrosis. Sphingosine kinase/sphingosine 1 phosphate and transforming growth factor-β/Smads pathways are both involved in pathogenesis of fibrosis in several organs by controlling differentiation of fibroblasts to myofibroblasts and the epithelial to-mesenchymal transition. However, their direct involvement in chronic colitis-associated fibrosis it is not yet known. In this study we evaluated the immunohistochemical expression of some proteins implicated in sphingosine kinase/sphingosine 1 phosphate and transforming growth factor-β/Smads pathways in Dextrane Sodium Sulphate (DSS)-induced colorectal fibrosis in mice. Compared to control mice, DSS-induced chronic colitis mice developed a marked intestinal fibrosis associated with a concomitant overexpression of TGF-β, p-Smad3, α-SMA, collagen I-III, SPHK1, RhoA, PI3K, Akt, p-Akt, p-mTOR. This study highlights the relationship between the two pathways and the possible role of SPHK1 in the intestinal fibrosis.  These results, if confirmed by in vitro studies, may have important clinical implications in the development of new therapeutical approaches in inflammatory bowel disease.

The human retina is a complex structure of organised layers of specialised cells that support the transmission of light signals to the visual cortex. The outermost layer of the retina, the retinal pigment epithelium (RPE), forms part of the blood retina barrier and is implicated in many retinal diseases. Lysophosphatidic acid (LPA) is a bioactive lipid exerting pleiotropic effects in various cell types, during development, normal physiology and disease. Its producing enzyme, AUTOTAXIN (ATX), is highly expressed by the pigmented epithelia of the human eye, including the RPE. Using human pluripotent stem cell (hPSC)-derived retinal cells, we interrogated the role of LPA in the human RPE and photoreceptors. hPSC-derived RPE cells express and synthesize functional ATX, which is predominantly secreted apically of the RPE, suggesting it acts in a paracrine manner to regulate photoreceptor function. In RPE cells, LPA regulates tight junctions, in a receptor-dependent mechanism, with an increase in OCCLUDIN and ZONULA OCCLUDENS (ZO)-1 expression at the cell membrane, accompanied by an increase in the transepithelial resistance of the epithelium. High concentration of LPA decreases phagocytosis of photoreceptor outer segments by the RPE. In hPSC-derived photoreceptors, LPA induces morphological rearrangements by modulating the actin myosin cytoskeleton, as evidenced by Myosin Light Chain l membrane relocation. Collectively, our data suggests an important role of LPA in the integrity and functionality of the healthy retina and blood retina barrier., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The bioactive lipid sphingosine-1-phosphate (S1P) is a main regulator of cell survival, proliferation, motility, and platelet aggregation, and it is essential for angiogenesis and lymphocyte trafficking. In that S1P acts as a second messenger intra- and extracellularly, it might promote cancer progression. The main cause is found in the high S1P concentration in the blood, which encourage cancer cells to migrate through the endothelial barrier into the blood vessels. The irreversible degradation of S1P is solely caused by the sphingosine-1-phosphate lyase (SGPL1). SGPL1 overexpression reduces cancer cell migration and therefore silences the endogenous S1P siren, which promotes cancer cell attraction-the main reason for metastasis. Since our previous metabolomics studies revealed an increased SGPL1 activity in association with successful breast cancer cell treatment in vitro, we further investigated expression and localization of SGPL1. Expression analyses confirmed a very low SGPL1 expression in all breast cancer samples, regardless of their subtype. Additionally, we were able to prove a novel SGPL expression in the cytoplasm membrane of non-tumorigenic breast cells by fusing three independent methods. The general SGPL1 downregulation and the loss of the plasma membrane expression resulted in S1P dependent stimulation of migration in the breast cancer cell lines MCF-7 and BT-20. Not only S1P stimulated migration could be repressed by overexpressing the natural SGPL1 variant not but also more general migratory activity was significantly reduced. Here, for the first time, we report on the SGPL1 plasma membrane location in human, non-malignant breast epithelial cell lines silencing the extracellular S1P siren in vitro, and thereby regulating pivotal cellular functions. Loss of this plasma membrane distribution as well as low SGPL1 expression levels could be a potential prognostic marker and a viable target for therapy. Therefore, the precise role of SGPL1 for cancer treatment should be evaluated.

Aberrant cell migration leads to the dispersal of malignant cells. The ubiquitous lipid mediator lysophosphatidic acid (LPA) modulates cell migration and is implicated in tumor progression. Yet, the signaling cascades that regulate LPA's effect on cell motility remain unclear. Using time-lapse imaging and quantitative analyses, we studied the role of signaling cascades that act downstream of LPA on the motility of MCF10CA1a breast cancer cells. We found that LPA alters cell motility via two major signaling pathways. The Rho/ROCK signaling cascade is the predominant pathway that increases E-Cadherin containing cell-cell adhesions and cortical arrangement of actomyosin to promote slow, directional, spatially coherent and temporally consistent movement. In contrast, Gα i/o - and Gα q/11 -dependent signaling cascades lessen directionality and support the independent movement of cells. The net effect of LPA on breast cancer cell migration therefore results from the integrated signaling activity of the Rho/ROCK and Gα i/o - and Gα q/11 -dependent pathways, thus allowing for a dynamic migratory response to changes in the cellular or microenvironmental context., (Published by Elsevier Inc.)

Rationale: Multilineage-differentiating stress enduring (Muse) cells, pluripotent marker stage-specific embryonic antigen-3 + cells, are nontumorigenic endogenous pluripotent-like stem cells obtainable from various tissues including the bone marrow. Their therapeutic efficiency has not been validated in acute myocardial infarction., Objective: The main objective of this study is to clarify the efficiency of intravenously infused rabbit autograft, allograft, and xenograft (human) bone marrow-Muse cells in a rabbit acute myocardial infarction model and their mechanisms of tissue repair., Methods and Results: In vivo dynamics of Nano-lantern-labeled Muse cells showed preferential homing of the cells to the postinfarct heart at 3 days and 2 weeks, with ≈14.5% of injected GFP (green fluorescent protein)-Muse cells estimated to be engrafted into the heart at 3 days. The migration and homing of the Muse cells was confirmed pharmacologically (S1PR2 [sphingosine monophosphate receptor 2]-specific antagonist JTE-013 coinjection) and genetically (S1PR2-siRNA [small interfering ribonucleic acid]-introduced Muse cells) to be mediated through the S1P (sphingosine monophosphate)-S1PR2 axis. They spontaneously differentiated into cells positive for cardiac markers, such as cardiac troponin-I, sarcomeric α-actinin, and connexin-43, and vascular markers. GCaMP3 (GFP-based Ca calmodulin probe)-labeled Muse cells that engrafted into the ischemic region exhibited increased GCaMP3 fluorescence during systole and decreased fluorescence during diastole. Infarct size was reduced by ≈52%, and the ejection fraction was increased by ≈38% compared with vehicle injection at 2 months, ≈2.5 and ≈2.1 times higher, respectively, than that induced by mesenchymal stem cells. These effects were partially attenuated by the administration of GATA4 -gene-silenced Muse cells. Muse cell allografts and xenografts efficiently engrafted and recovered functions, and allografts remained in the tissue and sustained functional recovery for up to 6 months without immunosuppression., Conclusions: Muse cells may provide reparative effects and robust functional recovery and may, thus, provide a novel strategy for the treatment of acute myocardial infarction., (© 2018 American Heart Association, Inc.)

Somatosensory neurons mediate responses to diverse mechanical stimuli, from innocuous touch to noxious pain. While recent studies have identified distinct populations of A mechanonociceptors (AMs) that are required for mechanical pain, the molecular underpinnings of mechanonociception remain unknown. Here, we show that the bioactive lipid sphingosine 1-phosphate (S1P) and S1P Receptor 3 (S1PR3) are critical regulators of acute mechanonociception. Genetic or pharmacological ablation of S1PR3, or blockade of S1P production, significantly impaired the behavioral response to noxious mechanical stimuli, with no effect on responses to innocuous touch or thermal stimuli. These effects are mediated by fast-conducting A mechanonociceptors, which displayed a significant decrease in mechanosensitivity in S1PR3 mutant mice. We show that S1PR3 signaling tunes mechanonociceptor excitability via modulation of KCNQ2/3 channels. Our findings define a new role for S1PR3 in regulating neuronal excitability and establish the importance of S1P/S1PR3 signaling in the setting of mechanical pain thresholds., Competing Interests: RH, BH, TM, SC, EL, RB, DB No competing interests declared, (© 2018, Hill et al.)

Sphingosine Kinase-2 (Sphk2) is responsible for the production of the bioactive lipid Sphingosine-1 Phosphate, a key regulator of tissue repair. Here we address the in vivo significance of Sphingosine Kinase -2 in renal inflammation/fibrosis in response to unilateral ureteral obstruction using both genetic and pharmacological strategies. Obstructed kidneys of Sphk2-/- mice showed reduced renal damage and diminished levels of the renal injury markers TGFβ1 and αSMA when compared to wild type controls. We found a consistently significant increase in anti-inflammatory (M2) macrophages in obstructed Sphk2-/- kidneys by flow cytometry and a decrease in mRNA levels of the inflammatory cytokines, MCP1, TNFα, CXCL1 and ILβ1, suggesting an anti-inflammatory bias in the absence of Sphk2. Indeed, metabolic profiling showed that the pro-inflammatory glycolytic pathway is largely inactive in Sphk2-/- bone marrow-derived macrophages. Furthermore, treatment with the M2-promoting cytokines IL-4 or IL-13 demonstrated that macrophages lacking Sphk2 polarized more efficiently to the M2 phenotype than wild type cells. Bone marrow transplant studies indicated that expression of Sphk2-/- on either the hematopoietic or parenchymal cells did not fully rescue the pro-healing phenotype, confirming that both infiltrating M2-macrophages and the kidney microenvironment contribute to the damaging Sphk2 effects. Importantly, obstructed kidneys from mice treated with an Sphk2 inhibitor recapitulated findings in the genetic model. These results demonstrate that reducing Sphk2 activity by genetic or pharmacological manipulation markedly decreases inflammatory and fibrotic responses to obstruction, resulting in diminished renal injury and supporting Sphk2 as a novel driver of the pro-inflammatory macrophage phenotype.

Microvesicles (MVs) are emerging as a new mechanism of intercellular communication by transferring cellular components to target cells, yet their function in disease is just being explored. However, the therapeutic effects of MVs in cartilage injury and degeneration remain unknown. We found MVs contained high levels of sphingosine-1-phosphate (S1P) compared with the original bone marrow mesenchymal stem cells (MSCs). The enrichment of S1P in MVs was mediated by sphingosine kinase 1 (SphK1), but not by sphingosine kinase 2 (SphK2). Co-culture of human chondrocytes with MVs resulted in increased proliferation of chondrocytes in vitro, which was mediated by activation of S1P receptor 1 (S1PR 1 ) expressed on chondrocytes. Meanwhile, MVs inhibited interleukin 1 beta-induced human chondrocytes apoptosis in a dose dependent manner. Furthermore, uptake of MVs by primary cultures of human chondrocytes was mediated by CD44 expressed by MVs. Anti-CD44 antibody significantly reduced the uptake of fluorescent protein-labeled MVs by chondrocytes. Further, blocking S1P by its neutralizing antibody significantly inhibited the therapeutic effects of MVs in vivo. Taken together, MVs showed therapeutic potential for treatment of clinical cartilage injury. This therapeutic potential is due to CD44-mediated uptake of MVs by chondrocytes and the S1P/S1PR 1 axis-mediated proliferative effects of MVs on chondrocytes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Lysophosphatidic acid (LPA) and LPA1 receptor signaling play a crucial role in the initiation of peripheral nerve injury-induced neuropathic pain through the alternation of pain-related genes/proteins expression and demyelination. However, LPA and its signaling in the brain are still poorly understood. In the present study, we revealed that the LPA5 receptor expression in corpus callosum elevated after the initiation of demyelination, and the hyperalgesia through Aδ-fibers following cuprizone-induced demyelination was mediated by LPA5 signaling. These data suggest that LPA5 signaling may play a key role in the mechanisms underlying neuropathic pain following demyelination in the brain., (Copyright © 2018 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

Background: Aspirin plays a crucial role in the prevention of cardiovascular diseases. We previously described that aspirin has effects beyond inhibition of platelet aggregation, as it inhibited thrombin-mediated release of sphingosine-1-phosphate (S1P) from human platelets. S1P is a bioactive lipid with important functions on inflammation and apoptosis. In endothelial cells (EC), S1P is a key regulator of cell migration. In this study, we aimed to analyze the effects of aspirin on platelet-induced EC migration., Methods: Human umbilical EC migration was measured by Boyden chamber assay. EC migration was induced by platelet supernatants of thrombin receptor-activating peptide-1 (AP1) stimulated platelets. To investigate the S1P receptor subtype that promotes EC migration, specific inhibitors of S1P receptor subtypes were applied., Results: S1P induced EC migration in a concentration-dependent manner. EC migration induced by AP1-stimulated platelet supernatants was reduced by aspirin. S1P1 receptor inhibition almost completely abolished EC migration induced by activated platelets. The inhibition of S1P2 or S1P3 receptor had no effect., Conclusion: Aspirin inhibits EC migration induced by activated platelets that is in part due to S1P and mediated by the endothelial S1P1 receptor. The clinical significance of this novel mechanism of aspirin action has to be investigated in future studies., (© 2017 S. Karger AG, Basel.)

Aldosterone has been identified as an important factor in obesity-associated hypertension. Here, we investigated whether sphingosine-1-phosphate (S1P), which has previously been linked to obesity, increases aldosterone release. S1P-induced aldosterone release was determined in NCI H295R cells in the presence of S1P receptor (S1PR) antagonists. In vivo release of S1P (100-300 µg/kg bw ) was investigated in pithed, lean Sprague Dawley (SD) rats, diet-obese spontaneous hypertensive rats (SHRs), as well as in lean or obese Zucker rats. Aldosterone secretion was increased in NCI H295R cells by S1P, the selective S1PR1 agonist SEW2871 and the selective S1PR2 antagonist JTE013. Treatment with the S1PR1 antagonist W146 or fingolimod and the S1PR1/3 antagonist VPbib2319 decreased baseline and/or S1P-stimulated aldosterone release. Compared to saline-treated SD rats, plasma aldosterone increased by ~50 pg/mL after infusing S1P. Baseline levels of S1P and aldosterone were higher in obese than in lean SHRs. Adrenal S1PR expression did not differ between chow- or CD-fed rats that had the highest S1PR1 and lowest S1PR4 levels. S1P induced a short-lasting increase in plasma aldosterone in obese, but not in lean SHRs. However, 2-ANOVA did not demonstrate any difference between lean and obese rats. S1P-induced aldosterone release was also similar between obese and lean Zucker rats. We conclude that S1P is a local regulator of aldosterone production. S1PR1 agonism induces an increase in aldosterone secretion, while stimulating adrenal S1PR2 receptor suppresses aldosterone production. A significant role of S1P in influencing aldosterone secretion in states of obesity seems unlikely., (© 2017 Society for Endocrinology.)

The bioactive sphingosine-1-phosphatephosphate (S1P) is present in plasma, bound to carrier proteins, and involved in many physiological processes, including angiogenesis, inflammatory responses, and vascular stabilization. S1P can bind to several G-protein-coupled receptors (GPCRs) activating a number of different signaling networks. At present, the dynamics and relative importance of signaling events activated immediately downstream of GPCR activation are unclear. To examine these, we used a set of fluorescence resonance energy transfer-based biosensors for different RhoGTPases (Rac1, RhoA/B/C, and Cdc42) as well as for heterotrimeric G-proteins in a series of live-cell imaging experiments in primary human endothelial cells. These experiments were accompanied by biochemical GTPase activity assays and transendothelial resistance measurements. We show that S1P promotes cell spreading and endothelial barrier function through S1PR 1 -Gα i -Rac1 and S1PR 1 -Gα i -Cdc42 pathways. In parallel, a S1PR 2 -Gα 12/13 -RhoA pathway is activated that can induce cell contraction and loss of barrier function, but only if Gα i -mediated signaling is suppressed. Our results suggest that Gα q activity is not involved in S1P-mediated regulation of barrier integrity. Moreover, we show that early activation of RhoA by S1P inactivates Rac1 but not Cdc42, and vice versa. Together, our data show that the rapid S1P-induced increase in endothelial integrity is mediated by a S1PR 1 -Gα i -Cdc42 pathway., (© 2017 Reinhard et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).)

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are potential stromal cells which are regarded as the most feasible stem cell group in cell therapy. The maintenance of cell survival without differentiation is important in cell transplantation and stem cell therapy. However, negative factors exist in cell transplantation. Lysophosphatidic acid (LPA) is a non-antigenic small molecule phospholipid which induced several fundamental cellular responses, such as cell proliferation, apoptosis and migration. In this study we aimed to explore the effects of LPA on the survival and differentiation of MSCs and its availability in cell therapy. We found that LPA stimulated hUC-MSC proliferation and protected hUC-MSCs from lipopolysaccharide (LPS) induced apoptosis. We also observed that CD29, CD44, CD73, CD90 and CD105 were expressed, whereas CD34 and CD45 were not expressed in hUC-MSCs, and these makers have no change in LPA containing medium, which indicated that LPA accelerated the survival of hUC-MSCs in an undifferentiating status. We also demonstrated that higher expressed LPAR1 involved in LPA stimulated cell survival action. LPA stimulated cell proliferation was associated with LPAR1 mediated G i/o -proteins/ERK1/2 pathway. On the other hand, LPA protected hUC-MSCs from LPS-induced apoptosis through suppressing caspase-3 activation by LPAR1 coupled with a G protein, but not G i/o or G q/11 in hUC-MSC. Collectively, this study demonstrated that LPA increased the proliferation and survival of hUC-MSCs without differentiation through LPAR1 mediated manner. Our findings provide that LPA as a anti-apoptotic agent having potential application prospect in cell transplantation and stem cell therapy.

The physiological functions of sphingosine 1-phosphate (S1P) and its pathological roles in various diseases are increasingly being elucidated. Particularly, a growing body of literature has implicated S1P in the pathogenesis of brain related disorders. With the deciphering of more intricate aspects of S1P signalling, there is also a need to reconsider the notion of S1P only as a determinant of cell survival and proliferation. Further the concept of 'S1P-ceramide' balance as the controlling switch of cellular fate and functions needs to be refined. In this review, we focus on the brain related functions of S1P with special focus on its role in synaptic transmission, neuronal autophagy and neuroinflammation. The review also attempts to bring out the multi-faceted nature of S1P signalling aspects that makes it a 'double edged sword'. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Undifferentiated nasopharyngeal carcinoma (NPC) is a cancer with high metastatic potential that is consistently associated with Epstein-Barr virus (EBV) infection. In this study, we have investigated the functional contribution of sphingosine-1-phosphate (S1P) signalling to the pathogenesis of NPC. We show that EBV infection or ectopic expression of the EBV-encoded latent genes (EBNA1, LMP1, and LMP2A) can up-regulate sphingosine kinase 1 (SPHK1), the key enzyme that produces S1P, in NPC cell lines. Exogenous addition of S1P promotes the migration of NPC cells through the activation of AKT; shRNA knockdown of SPHK1 resulted in a reduction in the levels of activated AKT and inhibition of cell migration. We also show that S1P receptor 3 (S1PR3) mRNA is overexpressed in EBV-positive NPC patient-derived xenografts and a subset of primary NPC tissues, and that knockdown of S1PR3 suppressed the activation of AKT and the S1P-induced migration of NPC cells. Taken together, our data point to a central role for EBV in mediating the oncogenic effects of S1P in NPC and identify S1P signalling as a potential therapeutic target in this disease. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd., (Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)